The problem of disposing of bulky waste materials is receiving increasing attention as existing land-fills reach capacity and the availability of additional land for waste disposal decreases. Reducing waste, such as tires, in size permits volume densification and reduces the requirements of subsequent processing.
Machines which utilize paired shearing wheels to shred waste material into smaller pieces have been developed. For example, U.S, Pat, Nos, 5,145,120, 4,901,929 and 4,607,800 to Barclay disclose machines in which rotating shearing wheels overlap at the edges of shear members on the wheels to cut into the waste material like giant knives. Other patents teaching this type of machine include U.S. Pat. No. 4,374,573 to Rouse et al., U.S. Pat. No. 3,991,944 to Baikoff and U.S. Pat. No. 3,931,935 to Holman. The aforementioned machines are "primary" shredders in the sense that whole tires may be fed into the machines for shredding. As best seen in the above-cited U.S. Pat. No. 4,901,929 to Barclay, annular hubs are attached to the outside diameter of drive shafts and the shear members are fixed to the hubs. The term "shredder" as used herein means a machine which reduces objects by shearing action.
One problem with the aforementioned shredders is their inability to reduce tires to sufficiently small pieces for use. As a result, it is often necessary to subject each tire to a plurality of sequential shredding steps. Shredders having only one shredding element make this task difficult and time consuming. With a single shredding element, it is necessary to reintroduce the tire segments into the shredder in order to further reduce the size of a shredded tire. This may be seen in U.S. Pat. No. 5,127,588 to Schmidt, where a feeder is provided with tines to force the tire into the teeth of a rotary cutting blade. The tines are spaced apart so that tire pieces exceeding a predetermined size are held in place. In this manner, the feeder may once again force these tire pieces into the cutting blade in order to reduce them to a desired size.
Many shredders, however, include a plurality of shredding elements and are designed to subject a tire to multiple shredding steps once the tire has been placed into it. In U.S. Pat. No. 4,714,201 to Rouse et al., a primary shredder shears a tire into primary pieces. The primary pieces are then fed into a secondary shredder via a conveyor belt, The second shredder produces secondary pieces which are smaller than the primary pieces and are fed into a hopper to sort the pieces according to size.
In U.S. Pat. No. 4,682,522 to Barclay, a tire shredder is disclosed having a plurality of rotary shears to sequentially segment a tire into many pieces. A first rotary shear cuts a tire into three annular segments. Each annular tire segment is then sheared into four arcuate parts by a second and a third rotary interleaving shear.
While the primary waste-reducing machines of the prior art significantly reduce the size of tires and the like, in some applications it is desirable to provide further reduction, while reducing the number of sequential shredding steps. Further, it is desirable to control the size of the scrap material produced from cutting the tires to obviate additional steps of sorting tire pieces according to size.
It is an object, therefore, of the present invention to provide a shredding apparatus capable of reducing the size of tires by producing a plurality of tire segments, while being able to vary the size of the segments produced.